Do these achievements to get the corresponding effect:
Hidden skater: complete the Pro Challenges to unlock Mindy, Frycook, Momo and Roger.
The Zone level: get all 90 packages
Turbo mode: get all the gaps on each level except The Zone
Pro Challenge: get all goals in a level.
Pro Skater animations: win the Pro Objective for that skater.
Alternate outfit: spend $40 at the skate shop.